Depends on your configuration. The most common, by far, is .223 Remington/5.56x45mm NATO.
5.56mm
Yes
Depends on markings on upper.
Depends on the ammo, the range, and the construction of the walls and the armoured cars. Most basic family homes - siding, insulation, drywall - won't even stop a regular handgun round.
The typical AR15 fires the same type of bullet as the M16: a .223 caliber (5.56mmx45mm NATO) round. There are AR-15 rifles that have special barrels made for a variety of popular cartridges, even the little .22LR.
Depends on your configuration. The most common, by far, is .223 Remington/5.56x45mm NATO.
1/2 28
Only 7.62x51. No other 7.62 round is compatible.
Shoot it or run round it
.308
Yes. Have fun paying for it then lugging it around, though - that's a whole lot of weight you're adding to the rifle.
Yes.